Method of and apparatus for deforming sheet metal



April s, 1958 w. ECKOLD 2,829,545

METHOD OF AND APPARATUS FOR DEFORM'ING SHEET METAL Filed March 19, 19532 Sheets-Sheet 1 Inveman' Wczzz'er Ec rozcz April 8, 1958 v w. ECKOLD2,829,545

METHOD OF AND APPARATUS FOR DEFORMING SHEET METAL Filed March 19, 1953 2Sheets-Sheet 2 Wa 2661 EM 02oz finished sheet metal articles.

United States Patent METHOD or AND APPARATUS FOR DEFORMING SHEET METALWalter Eckold, St. Andreasberg, Sperrluttertal, Oberharz, Germany Thisinvention relates to a method of and an apparatus for working out orre-forming plastic deformations in sheet metal.

Both manual and mechanical methods of deforming sheet metal are known.In manual deformation, chasing hammers have hitherto been generallyemployed, the principle of which has also been applied to mechanicaldeformation. Apart from its uneconomical nature, this primitive methodis attended by noise which renders all communication between the workspersonnel extremely difiicult, particularly when a mechanical chasinghammer is employed.

In a further known method of producing deformations in sheet metal byhand, the metal sheets are driven into a block havinga hemisphericalcavity by means of large wooden or rubber hammers. In the correspondingmechanical method, the sheet is driven by means of apunch having ahemispherical or spherical contact surface, in any desired number ofworking operations, into a die fashioned hemispherically to correspondwith the form of a punch. Such tools, which consist mainly of wood,require a large mounting to accommodate varying diameters and are inaddition subject to considerable wear. Moreover, the finished articlesrequire additional finishing work, thus in many cases increasing thecost of the process.

Based on this experience, specially fashioned tools have already beendeveloped which deform the material by drawing or swaging, but theapplication thereof has been limited to the deformation of the edgezones of semi- Here again, exceptionally high installation costs areinvolved in cases where the deforming work is carried out with the aidof presses or rolls.

The object of the invention is to make mechanical sheet-metaldeformation more universally applicable by According to the invention,this is rendered possible by causing hollow punches having astrip-shaped contact surface and an external configuration adapted tothe forms in question to act on the sheet-metal parts to be deformed,the said hollow punches producing a flow of the material in that part ofthe surface which is encompassed by the hollow punch in each case andthus gradually working out the desired forms, or smoothing outundesirable deformations, in a succession of working operations, thesheet metal being systematically guided.

The deformation produced by the hollow punch in each case is preferablyassisted by a correspondingly shaped counter-punch, which may beconstructed as a fixed or oppositely movable abutment.

The hollow punch for carrying out the described process of deformationmay itself be rigid throughout or so constructed that its contactsurface yields resiliently, resulting in a tendency of that part of thesurface of the sheet metal which is encompassed by the hollow punch tocontract or expand, depending on the direction of the springing action.

As examples of the invention several hollow punches will now bedescribed in greater detail with reference to the accompanying drawingsof which:

Figures 1 and 2 show hollow punches of frusto-conical form,

Figures 3 and 4 show modified punches with means for increasing thedeformation,

Figures 5 and 6 show hollow punches capable of eifecting both swagingand drawing,

Figures 7 and 8 show further different punches,

Figures 9 and 10 show punches of differing profiles and Figures 11 and12 show details of a complete punch assembly.

The hollow punches 1 and 2 illustrated in Figs. 1 and 2 are offrusto-conical form. Theannular contact surfaces 3 of the punch 1 shownin Fig. 1 contract inwardly somewhat under the pressure of the punch,While in the case of the punch 2 shown in Fig. 2 they expand outwardly.Due to this movement the fiow of the material within that part of thesurface of the sheet metal which is encompassed by the hollow punch willbe assisted by a swaging action in Fig. l and a drawing action in Fig.2.

This slight deflection of the hollow punches is increased in the formsshown in Figs. 3 and 4 due to the formation of slots 6 in the jackets ofthe swaging tool 4 and of the drawing tool 5, whereby a greaterdeflection of the tools results from the same load.

Figs. 5 and 6 show two constructions of hollow punches by which acombined swaging and drawing action is produced. In the hollow punch 7shown in Fig. 5, the outer contact surface 8 effects the swaging whilethe inner contact surface 9 effects the drawing. Conversely, in thehollow punch 10 shown in Fig. 6, the outer contact surface 11 effects adrawing and the inner contact surface 12 a swaging. Both actions areincreased by slots 13.

In the forms shown in Figs. 7 and 8, the hollow punch consists of aslotted ring which is constricted or widened out by a form of guiding inthe mounting. in the form shown in Fig. 7, the widening is effected .bythin steel plates 15 fitted at an incline, while in the form shown inFig. 8 the constriction is effected by the conical surfaces 16, whichbecome effective under bearing pressure.

In Figs. 9 and 10, two constructional forms having a number of profilesare illustrated, the profiles Ibeing ovalin the punch 17 shown in Fig. 9and extending in concentric circles in the punch 18 shown in Fig. 10. Incontrast to the punch constructions hereinbefore described, the profileshere are rigid, so that the flow of material is initiated only by thepressure of the contact surface of the profiles on the sheet-metalarticles.

'In the example shown in Figures 11 and 12., the annular contact surfactof the hollow punch is subdivided into twelve segments 21, each of whichis mounted on one or more thin steel plates or laminations 22. The steelplates here bear in recesses 23 in the lower side of each segment 21 andin the upper side of an inserted ring 24, which is fitted by means of anextension 25 in the recess 26 in the supporting member 27.

The steel plates 22, which are in this case inwardly inclined for aswaging operation are embedded over their free length in a resilientmass 28 which, on removal of a vertically acting working pressure fromthe segments 21, returns the plates to their inclined initial position.

In order in this case to utilise the resiliency fully for the return ofthe steel plates, that is to say, to prevent them from yieldingoutwardly and inwardly, the resilient mass is encircled or internallysupported by retaining rings 29. Finally, the sleeve 30 is pushed on tothe tool.

In order to centre the ring of segments 21, a centering member 31 isalso fitted in countersunk fashion, the centering member overlapping,and thus holding fast, by means of a projecting edge 32 an inner steppedportion 33 on the segments 21. Suflicient lateral clearance for theinwardly directed working movement of the segments 21 is left, which isfilled by a rubber packing 34 which at the same time assists in thereturn of thesegments into their initial position.

Finally, narrow rubber strips 35 are disposed between the individualsegments 21 in order to protect the interior of the tool against theingress of dirt and moisture. Owing to the fact that the centeringmember is detachably fitted by means of a screw 36, the interchanging ofthe punch parts is made easier.

The invention is not limited to the embodiments described andillustrated by way of example. These are merely intended to show theunderlying idea of the invention, residing in the subdivision of themore or less closed contact surface of the hollow punch into individualsegments which carry out their working movements independently of oneanother and combine to produce the flow of the material in that part ofthe surface which is encompassed by the hollow punch.

The described hollow punches may work on smooth or profiled anvilsurfaces or may co-operate with identically fashioned counter-punches,whereby the distortion is further assisted.

It is specifically to be noted that the construction of the hollowpunches is not in any way limited and that the form thereof must beadapted to the particular deforming work to be performed. The onlyfactor always essential to the method according to the invention residesin that the hollow punch, regardless of whether it is rigid, elastic orprovided with guide means, encompasses throughout the deformingoperation a part of the surface of the sheet metal article, within whicha flow or displacement of the material is set up by the pressure aloneor with the assistance of movements of the hollow punch itself resultingin a gradual working-out or smoothing out of plastic deformations.

What I claim is:

1. A tool for changing the dimensions of sheet metal along its planarextent comprising a shank, and an integral hollow cup-shaped punchcomposed of inner and outer trusts-conical continuous walls, saidfrusto-conical punch having one of its bases secured to said shank, andthe other of its bases forming a continuous annular edge for engagementwith a sheet of metal, the slant height of said frusto-conical punch andthe thickness between the walls thereof being such that said continuousedge when forced against a sheet of metal will deform and change theplanar dimension of the sheet of metal.

2. A tool according to claim 1, in which the annular edge constitutesthe larger of said' bases to create a stretching action on thesheet ofmetal.

3. The tool according to claim 1, in which said annular edge constitutesthe smallest of said bases to create a compressive action 011 the sheetof metal.

References Cited in the file of this patent UNITED STATES PATENTS468,613 Frist Feb. 9, 1892 633,316 Heinz Sept. 19, 1899 1,012,992 DavisDec. 26, 1911 2,010,996 Junkers Aug. 13, 1935 2,060,675 Kirchner Nov.10, 1.936 2,407,573 .Nelson Sept. 10, 1946 2,428,173 Moore Sept. 30,1947 2,649,820 Hunt Aug. 25, 1953

